Garth tsunami
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The Garth tsunami is a likely prehistoric tsunami off the Shetland Islands that may have occurred 5,500 years ago (3,500 B.C.). Its origin is unknown; impact events, earthquakes, and submarine landslides similar to the Storegga Slide 8,100 years ago (6,100 B.C.) have been proposed as factors contributing to the event. Evidence suggests a run-up of more than 10 metres (33 ft) in the Shetland Islands. It probably had great impact on coastal communities in the region; mass burials dating approximately to that time in the Shetland and Orkney Islands have been interpreted to host its fatalities.
The tsunami is named after Garth Loch.[1] It likely took place approximately 5,500 years ago and also is known as the "5,500 BP event".[2] It generated a run-up of more than 10 metres (33 ft) in the Shetland Islands.[3] This tsunami is one of three thought to have hit Scotland during the Holocene[4] although the occurrence of this or a later one are considered uncertain.[5]
Deposits
Deposits from the tsunami have been recovered at Garth, South Nesting, in Garth Loch and Loch of Benston and Whale Firth;[6][7] originally it was discovered at Sullum Voe, Shetland.[2] Further evidence of environmental changes possibly caused by a tsunami 5,500 years ago have been identified at West Voe.[8] Its deposits resemble those created by the tsunamis generated by the Storegga Slide 8,100 years ago. Evidence, later questioned, from this tsunami has also been found in Bergsøy, Norway,[3][9] the second ocean transgression in southwestern Norway may be the Garth tsunami,[10] and potential traces have been found in coastal lakes of Norway. No evidence of the tsunami has been found in Scotland or the Orkney Islands, which would be shielded by the Shetland Islands from a tsunami that originated at the Norwegian continental slope.[11] Landscape changes in the Orkney Islands that occurred 5,500 years ago may be a consequence either of the tsunami or of a period of increased storm activity at that time.[12]
